Conductive mechanism
Stanley A. Gelfand in Hearing, 2017
Head-related transfer functions depend on the direction of the sound source. The fundamental nature of this azimuth effect is illustrated for two representative directions in Figure 3.2. Here, we are concerned with the sound reaching the right eardrum when it is presented from a loudspeaker at an azimuth of 45° to the right compared to being presented from a speaker at 45° to the left. The right ear is the near ear when the sound comes from the right (same side of the head), and it is the far ear when the sound comes from the left (the opposite side of the head). Note that the sound level increases going from the far ear, and that there are differences in the details of the shapes of the two curves. Physical factors of this type provide the basis for sound localization in space (see Chapter 13).
Special Senses
Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard in Toxicologic Pathology, 2018
The ear can be divided into three parts: the external ear, middle ear, and inner ear. The external ear consists of the pinna (auricle) and the external ear canal (external auditory meatus), which ends medially at the external surface of the tympanic membrane (ear drum). The structures of the external ear are supported by auricular cartilage, and the secretions from the sebaceous and ceruminous glands contribute to the formation of cerumen. In rodents, Zymbal’s gland is a sebaceous gland located anterior and ventral to the external ear canal. Pathologic changes of the external ear can involve the skin or specific structures of the external ear (Kelemen 1978). Inflammation of the external auditory canal is usually not an issue in toxicologic studies unless clinical signs, such as shaking of the head or ear scratching, are observed. When inflammation does occur, it is characterized by thickening of the wall of the external auditory canal from edema, and the presence of a tan or brown crusty exudate within the canal (Gad 2007). One cause can be ear mites (e.g., Psoroptes cuniculi in rabbits or Otodectes cynotis in dogs). Auricular chondritis is a spontaneous condition reported in several strains of rats that appears as nodular or diffuse thickening of the pinna by granulomatous inflammation of fibrochondrous to chondroosseous tissue (Chiu 1991; Kitagaki et al. 2003). Differential diagnoses include chondrolysis and neoplasms.
Ears
Marie Lyons, Arvind Singh in Your First ENT Job, 2018
The external ear consists of the pinna and the outer ear canal (seeFigure 1.1). The outer third of the ear canal is cartilaginous, hair-bearing and wax-producing. It is also not particularly sensitive, which makes it relatively easy to inspect with an auroscope. The inner third is bony and exquisitely sensitive. Push too deep into the bony ear canal and the patient will certainly protest! The outer ear canal ends at the eardrum, which in a healthy ear is a pale grey structure (seeFigure 1.2). The most obvious features are the handle of the malleus and antero-inferiorly the cone of light (see below). When you are shown a picture of the eardrum you can always identify which side it is on by the direction in which the malleus is pointing. If the eardrum is on the right side, the malleus will point upwards and superiorly to the right from the middle of the eardrum. If it is on the left side, the malleus will point to the left (amaze your boss at quizzes!).
Studying subjective hearing loss in older adults measured by speech, spatial, and quality of hearing scale within the framework of the ICF core set for hearing loss
Published in Hearing, Balance and Communication, 2022
Noteworthy, as ear structures and functions are responsible for hearing and balance, cortical networks during auditory activities (dynamic and stationary) not only receiving acoustical stimuli but also receiving other sensory stimuli including, the vestibular sensation of rotational or translational acceleration of the head. This is consistent with the overwhelming evidence from animal studies that the ear system transmits specific types of information about hearing and balance to brain structures such as the hippocampus. Hence, perceptual sensations due to structural/functional damage of the ear organ can lead to SHL or dizziness or SHL and dizziness. From audiologic perspective, as older adults with impaired hearing experienced auditory-related activity limitations, dizzy patients usually experienced motor-related activities limitations.
The applications of targeted delivery for gene therapies in hearing loss
Published in Journal of Drug Targeting, 2023
Melissa Jones, Bozica Kovacevic, Corina Mihaela Ionescu, Susbin Raj Wagle, Christina Quintas, Elaine Y. M. Wong, Momir Mikov, Armin Mooranian, Hani Al-Salami
The complex structure of the mammalian ear is divided into three primary sections, classified as the outer, middle, and inner ear, with all parts required to work in an organised, controlled synergistic nature for hearing to occur. Focus here will be on the inner ear, which has roles in both hearing and balance [38]. The inner ear contains the cochlea where auditory signals are transduced. Located within the cochlea are three ducts, termed the scala vestibule, scala media, and scala tympani. Within the scala media of the cochlea, the organ of Corti is positioned, with the primary function of transducing auditory signals. The organ of Corti contains both inner and outer hair cells, being mechanosensory hair cells arranged in rows, with three rows of outer hair cells and one row of inner hair cells in the luminal half of the organ. Also located within are supporting cells of a non-sensory nature, positioned throughout the basement membrane to the luminal surface in a highly organised pattern [23,39,40].
High-resolution computed tomography temporal bone imaging in achondroplasia
Published in Baylor University Medical Center Proceedings, 2021
Puneet S. Kochar, Priti Soin, Ayah Megahed
The predominant temporal bone imaging feature is rotation and upward tilting of the petrous temporal bones, giving a “towered” petrous ridges appearance.6,7 The IAC-IAC angle is reduced, ranging from 110° to 129° (normal 157–175°). The IACs are normal. Additionally, the cochlea rotates in relation to the middle ear cavity, leading to a vertically oriented geniculate ganglion. However, the cochlea is morphologically normal. The vestibules are also rotated, leading to a downward-directed oval window.6 Middle ear ossicles are usually normal in size and morphology. However, secondary to the rotation, the malleus body and long process of incus project into the axial images, giving a broader ice cream cone appearance. The external acoustic canal (EAC) is rotated to a lesser extent than the medial temporal bone, leading to an abnormal orientation of the EAC and tympanic membrane with the lateral labyrinth wall at the time of clinical exam. Instead of encountering the promontory from the EAC as the tympanic membrane is reflected, the examiner is either not able to see the promontory or at best is able to see its inferior margin. The bony structure in the way is the scutum. On imaging, the scutum points downwards below the level of the promontory. The Körner septum becomes more horizontally rotated.6 The carotid canal is foreshortened with medialization of the distal ends. The ascending portion of the carotid canal is medially angulated instead of having a normal vertical orientation.6
Related Knowledge Centers
- Auricle
- Ear Canal
- Hearing
- Inner Ear
- Middle Ear
- Ossicles
- Outer Ear
- Tympanic Cavity
- Vestibular System
- Sense of Balance